The /a regular expression modifier restricts \s to match precisely the five characters [ \f\n\r\t],
\d to match precisely the 10 characters [0-9],
\w to match precisely the 63 characters [A-Za-z0-9_],
and the Posix ([[:posix:]]) character classes to match only the appropriate ASCII characters.
The complements,
of course,
match everything but; and \b and \B are correspondingly affected.
Otherwise,
/a behaves like the /u modifier,
in that case-insensitive matching uses Unicode semantics; for example,
"k" will match the Unicode \N{KELVIN SIGN} under /i matching,
and code points in the Latin1 range,
above ASCII will have Unicode semantics when it comes to case-insensitive matching.
Like its cousins (/u,
/l,
and /d),
and in spite of the terminology,
/a in 5.14 will not actually be able to be used as a suffix at the end of a regular expression (this restriction is planned to be lifted in 5.16).
It must occur either as an infix modifier,
such as (?a:...) or ((?a)...,
or it can be turned on within the lexical scope of use re '/a'.
Turning on /a turns off the other "character set" modifiers.

With this release,
Perl is adopting a model that any unsigned value can be treated as a code point and encoded internally (as utf8) without warnings -- not just the code points that are legal in Unicode.
However,
unless utf8 warnings have been explicitly lexically turned off,
outputting or performing a Unicode-defined operation (such as upper-casing) on such a code point will generate a warning.
Attempting to input these using strict rules (such as with the :encoding('UTF-8') layer) will continue to fail.
Prior to this release the handling was very inconsistent,
and incorrect in places.
Also,
the Unicode non-characters,
some of which previously were erroneously considered illegal in places by Perl,
contrary to the Unicode standard,
are now always legal internally.
But inputting or outputting them will work the same as for the non-legal Unicode code points,
as the Unicode standard says they are illegal for "open interchange".

In "User-Defined Character Properties" in perlunicode,
it says you can create custom properties by defining subroutines whose names begin with "In" or "Is".
However,
perl doesn't actually enforce that naming restriction,
so \p{foo::bar} will call foo::Bar() if it exists.

This commit finally enforces this convention.
Note that this broke a number of existing tests for properties,
since they didn't always use an Is/In prefix.

CPAN::Meta::YAML 0.003 has been added as a dual-life module.
It supports a subset of YAML sufficient for reading and writing META.yml and MYMETA.yml files included with CPAN distributions or generated by the module installation toolchain.
It should not be used for any other general YAML parsing or generation task.

HTTP::Tiny 0.009 has been added as a dual-life module.
It is a very small,
simple HTTP/1.1 client designed for simple GET requests and file mirroring.
It has has been added to enable CPAN.pm and CPANPLUS to "bootstrap" HTTP access to CPAN using pure Perl without relying on external binaries like curl or wget.

JSON::PP 2.27103 has been added as a dual-life module,
for the sake of reading META.json files in CPAN distributions.

Module::Metadata 1.000003 has been added as a dual-life module.
It gathers package and POD information from Perl module files.
It is a standalone module based on Module::Build::ModuleInfo for use by other module installation toolchain components.
Module::Build::ModuleInfo has been deprecated in favor of this module instead.

Perl::OSType 1.002 has been added as a dual-life module.
It maps Perl operating system names (e.g.
'dragonfly' or 'MSWin32') to more generic types with standardized names (e.g.
"Unix" or "Windows").
It has been refactored out of Module::Build and ExtUtils::CBuilder and consolidates such mappings into a single location for easier maintenance.

Further improvements have been made to guard against newline injections in headers.

Compress::Raw::Bzip2 has been upgraded from version 2.031 to 2.033

Compress::Raw::Zlib has been upgraded from version 2.030 to 2.033

CPAN has been upgraded from version 1.94_62 to 1.94_63

CPANPLUS has been upgraded from version 0.9010 to 0.9011

CPANPLUS::Dist::Build has been upgraded from version 0.50 to 0.52

DB_File has been upgraded from version 1.820 to 1.821

Encode has been upgraded from version 2.40 to 2.42.
Now,
all 66 Unicode non-characters are treated the same way U+FFFF has always been treated; if it was disallowed,
all 66 are disallowed; if it warned,
all 66 warn.

File::Fetch has been upgraded from version 0.28 to 0.32

IO::Compress has been upgraded from version 2.030 to 2.033

IPC::Cmd has been upgraded from version 0.66 to 0.68

Log::Message has been upgraded from version 0.02 to 0.04

Log::Message::Simple has been upgraded from version 0.06 to 0.08

Module::Load::Conditional has been upgraded from version 0.38 to 0.40

Object::Accessor has been upgraded from version 0.36 to 0.38

Params::Check has been upgraded from version 0.26 to 0.28

Pod::LaTeX has been upgraded from version 0.58 to 0.59

Socket has been updated with new affordances for IPv6,
including implementations of the Socket::getaddrinfo() and Socket::getnameinfo() functions,
along with related constants.

Previously,
if none of the gethostbyaddr,
gethostbyname and gethostent functions were implemented on a given platform,
they would all die with the message 'Unsupported socket function "gethostent" called',
with analogous messages for getnet* and getserv*.
This has been corrected.

The opcode bodies for chop and chomp and for schop and schomp have been merged.
The implementation functions Perl_do_chop() and Perl_do_chomp(),
never part of the public API,
have been merged and moved to a static function in pp.c.
This shrinks the perl binary slightly,
and should not affect any code outside the core (unless it is relying on the order of side effects when chomp is passed a list of values).

Some of the flags parameters to the uvuni_to_utf8_flags() and utf8n_to_uvuni() have changed.
This is a result of Perl now allowing internal storage and manipulation of code points that are problematic in some situations.
Hence,
the default actions for these functions has been complemented to allow these code points.
The new flags are documented in perlapi.
Code that requires the problematic code points to be rejected needs to change to use these flags.
Some flag names are retained for backward source compatibility,
though they do nothing,
as they are now the default.
However the flags UNICODE_ALLOW_FDD0,
UNICODE_ALLOW_FFFF,
UNICODE_ILLEGAL,
and UNICODE_IS_ILLEGAL have been removed,
as they stem from a fundamentally broken model of how the Unicode non-character code points should be handled,
which is now described in "Non-character code points" in perlunicode.
See also "Selected Bug Fixes".

Certain shared flags in the pmop.op_pmflags and regexp.extflags structures have been removed.
These are: Rxf_Pmf_LOCALE,
Rxf_Pmf_UNICODE,
and PMf_LOCALE.
Instead there are encodes and three static in-line functions for accessing the information: get_regex_charset(),
set_regex_charset(),
and get_regex_charset_name(),
which are defined in the places where the original flags were.

A new option has been added to pv_escape to dump all characters above ASCII in hexadecimal.
Before,
one could get all characters as hexadecimal or the Latin1 non-ASCII as octal

Generate pp_* prototypes in pp_proto.h,
and remove pp.sym

Eliminate the #define pp_foo Perl_pp_foo(pTHX) macros,
and update the 13 locations that relied on them.

regen/opcode.pl now generates prototypes for the PP functions directly,
into pp_proto.h.
It no longer writes pp.sym,
and regen/embed.pl no longer reads this,
removing the only ordering dependency in the regen scripts.
opcode.pl is now responsible for prototypes for pp_* functions.
(embed.pl remains responsible for ck_* functions,
reading from regen/opcodes)

The handling of Unicode non-characters has changed.
Previously they were mostly considered illegal,
except that only one of the 66 of them was known about in places.
The Unicode standard considers them legal,
but forbids the "open interchange" of them.
This is part of the change to allow the internal use of any code point (see "Core Enhancements").
Together,
these changes resolve # 38722,
# 51918,
# 51936,
# 63446

Sometimes magic (ties,
tainted,
etc.) attached to variables could cause an object to last longer than it should,
or cause a crash if a tied variable were freed from within a tie method.
These have been fixed [perl #81230].

Most I/O functions were not warning for unopened handles unless the 'closed' and 'unopened' warnings categories were both enabled.
Now only use warnings 'unopened' is necessary to trigger these warnings (as was always meant to be the case.

<expr> always respects overloading now if the expression is overloaded.

Due to the way that '<> as glob' was parsed differently from '<> as filehandle' from 5.6 onwards,
something like <$foo[0]> did not handle overloading,
even if $foo[0] was an overloaded object.
This was contrary to the documentation for overload,
and meant that <> could not be used as a general overloaded iterator operator.

Destructors on objects were not called during global destruction on objects that were not referenced by any scalars.
This could happen if an array element were blessed (e.g.,
bless \$a[0]) or if a closure referenced a blessed variable (bless \my @a; sub foo { @a }).

Now there is an extra pass during global destruction to fire destructors on any objects that might be left after the usual passes that check for objects referenced by scalars [perl #36347].

A long standing bug has now been fully fixed (partial fixes came in earlier releases),
in which some Latin-1 non-ASCII characters on ASCII-platforms would match both a character class and its complement,
such as U+00E2 being both in \w and \W,
depending on the UTF-8-ness of the regular expression pattern and target string.
Fixing this did expose some bugs in various modules and tests that relied on the previous behavior of [[:alpha:]] not ever matching U+00FF,
"LATIN SMALL LETTER Y WITH DIAERESIS",
even when it should,
in Unicode mode; now it does match when appropriate.
[perl #60156].

If you find what you think is a bug,
you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ .
There may also be information at http://www.perl.org/ ,
the Perl Home Page.

If you believe you have an unreported bug,
please run the perlbug program included with your release.
Be sure to trim your bug down to a tiny but sufficient test case.
Your bug report,
along with the output of perl -V,
will be sent off to perlbug@perl.org to be analysed by the Perl porting team.

If the bug you are reporting has security implications,
which make it inappropriate to send to a publicly archived mailing list,
then please send it to perl5-security-report@perl.org.
This points to a closed subscription unarchived mailing list,
which includes all the core committers,
who be able to help assess the impact of issues,
figure out a resolution,
and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported.
Please only use this address for security issues in the Perl core,
not for modules independently distributed on CPAN.